Outline Bio 105: Muscular System Lecture 11 Chapter 6 Characteristics of muscles 3 types of muscles Functions of muscles Structure of skeletal muscles Mechanics of muscle contraction Energy sources for muscle contraction 1 2 Muscular System Types of Muscles 3 different types of muscles Muscles cells Muscles fibers ALL muscle tissues contract Made up of Muscle cells (muscle fibers) Connective tissue Blood vessels Nerves Smooth Cardiac Skeletal Things to know Voluntary vs Involuntary Location Function 3 4 Smooth Muscle Cardiac Muscle Involuntary Walls of many internal organs Digestive tract, Respiratory system, Blood vessels Function Aid in the function of other organs Involuntary Only found in heart wall Functions Contracting to force blood from the heart into the arteries 5 6 1
Skeletal Muscles Voluntary Attached to the skeleton Usually work in pairs Function Five different functions 7 8 11-2 Skeletal Muscles Work in pairs Antagonistic pairs One muscle contracts One muscle relaxes Attached to bone by tendons Usually attached to two bones on opposite sides of a joint 9 10 Origin Skeletal Muscles Attached to the bone that remains stationary during movement Insertion Attached to the bone that moves Skeletal Muscles Work in Pairs The biceps contracts and pulls the forearm up, flexing the arm. The relaxed triceps is stretched. Origin of muscle: attachment of muscle to less moveable bone (a) Flexion Insertion of muscle: attachment of muscle to more moveable bone 11 12 Figure 6.1a 2
Skeletal Muscle Functions 1) Support the body 2) Movement of bones and other tissues 3) Help maintain a constant body temperature 4) Helps move blood through the veins and lymphatic fluid through the lymphatic vessels 5) Help to protect vital organs and stabilize joints Review Questions What muscle(s) are voluntary? What muscle(s) are involuntary? Where are smooth muscles found? 13 14 Structure of Skeletal Muscles Covered by fascia Contains Bundles of skeletal muscle fibers (cells) Fascicles Covered by connective tissue Blood vessels and nerves between the fascicles Structure of Skeletal Muscles Skeletal muscle A muscle cell consists of consists of many many bundles myofibrils. of muscle cells. A bundle of muscle cells is called a fascicle. (a) A section of a skeletal muscle The striped (striated) appearance of a skeletal muscle cell is due to the regular arrangement of myofilaments. 15 16 Copyright (b) 2009 A Pearson light micrograph Education, Inc. of a longitudinal view of skeletal muscle cells Figure 6.3a b Sarcomeres The striped (striated) appearance of a skeletal muscle cell is due to the regular arrangement of myofilaments. (b) A light micrograph of a longitudinal view of skeletal muscle cells Z line Muscle Cells Long cells called muscle fibers Muscle fiber Composed of long thin myofibrils One sarcomere 17 Copyright 2009 (c) Pearson A diagram Education, and Inc. electron micrograph of a myofibril Figure 6.3b c 18 3
a. T tubule b. Sarcoplasmic reticulum c. myofibril Muscle Cells d. Z line 19 Copyright Education, e. sarcomere Inc. f. sarcolemma 2009 Pearson 20 Myofibrils Bundles of myofilaments that contract Myofilaments Made of actin and myosin filaments Muscle contraction Myofilaments slide past one another causing sarcomeres to shorten Muscle Cell Components Sarcolemma Plasma membrane (Cell membrane) Sarcoplasm Similar to cytoplasm Contains large amount of stored glycogen and myoglobin Myoglobin Oxygen binding protein Similar to hemoglobin Sarcoplasmic reticulum Similar to endoplasmic reticulum One function = store Ca ++ Muscle Cell Components Unique features Multiple nuclei Transverse Tubules (T tubules) Extension of sarcolemma that come into contact with the sarcoplasmic reticulum 21 22 Review Question What do you call a bundle of muscle cells? 23 24 4
Sarcomeres Z line 25 2 types of myofilaments Actin filaments Myosin filaments Sarcomere Structural unit of these myofilaments Goes between 2 dark lines (Z lines) Z lines = protein sheets where the actin filaments attach 26 One sarcomere (c) A diagram and electron micrograph of a myofibril Z line Z line One sarcomere Actin Myosin (d) A sarcomere, the contractile unit of a skeletal muscle, contains actin and Copyright 2009 myosin Pearson myofilaments. Education, Inc. Figure 6.3c d Actin Filaments Thin filaments Formed by 2 intertwining strands of the protein actin Myosin Filaments Thick filaments Made of the protein myosin Shaped like a golf club, with a round head Neuron signals muscle to contract Myosin heads attach to the actin Then pull actin toward the center of the sarcomere Myosin heads detach 27 28 Sarcomeres Neuromuscular Junction 29 30 Figure 6.4 Figure 6.7 (1 of 2) 5
https://www.youtube.com/watch?v=420 1SrN0WlY 31 32 1) Action potentials are transmitted through the neurons 2) Neurotransmitters are released 3) Neurotransmitters bind to the receptor on the sarcolemma 4) The receptors are ion channels that open 5) An action potential travels through the T tubules 6) The action potential goes to the sarcoplasmic reticulum 7) The sarcoplasmic reticulum releases Ca ++ 8) The Ca ++ binds to the troponin on the actin filament 9) Opens binding site for the myosin to attach 10) Myosin binds to the actin 11) Myosin slides past the actin 33 34 Sarcomeres Sarcomeres 35 36 Figure 6.6 (1 of 2) Figure 6.6 (2 of 2) 6
ATP is needed for the myofilaments to slide past each other 37 38 Review Questions What is the oxygen binding protein found only in muscles? What ion is required for the myofilaments to bind to each other? Where is the calcium stored? 39 40 ATP is needed for the myofilaments to slide past each other 41 42 7
Energy Source Muscle contraction requires a lot of energy in the form of ATP Muscles get their ATP from 3 sources 1) Breakdown of creatine phosphate 2) Cellular respiration 3) Fermentation 43 44 Creatine Phosphate Regenerates ADP to make ATP Quick energy for a few seconds 1 ATP produced per creatine phosphate Oxygen is not needed Resting muscle ATP in turn regenerates creatine phosphate Creatine Phosphate - Direct Phosphorylation 45 46 Cellular Respiration Fermentation In mitochondria Glucose broken down to produce ATP Oxygen is needed on the electron transport chain Carbon dioxide is produced Can provide energy for hours Produces 36 ATP per glucose molecule Glycolysis only Glucose is broken down to lactic acid Oxygen is not required Produces lactic acid Provides energy for 30 to 60 seconds 2 ATP produced per glucose molecule 47 48 8
ATP Comes from Many Sources ATP Comes from Many Sources 6 seconds 10 seconds 30 40 seconds ATP stored in muscles ATP formed from creatine phosphate and ADP ATP generated from glycogen stored in muscles and broken down to form glucose Oxygen limited Glucose oxidized to lactic acid 49 50 Figure 6.10 Figure 6.10 (1 of 2) ATP Comes from Many Sources Energy Summary Creatine Phosphate Breakdown Cellular Respiration Fermentation Requires Oxygen No Yes No 51 End of exercise ATP generated from glycogen stored in muscles and broken down to form glucose Oxygen present Heart beats faster to deliver oxygen more quickly Myoglobin releases oxygen After prolonged exercise Oxygen debt paid back Breathe heavily to deliver oxygen Lactic acid used to produce ATP Creatine phosphate restored Oxygen restored to myoglobin Glycogen reserves restored Figure 6.10 (2 of 2) 52 Produces CO2 # of ATP produced No Yes No 1 36 2 Duration 30 seconds Hours 30-60 seconds Review Question Which energy source would a long distance runner mainly use on a run that lasted for hours? Which energy source would a sprinter use in the first 5 seconds of the race? Important Concepts What are the three types of muscles? Where are they found? Are they under voluntary or involuntary control What are the functions of skeletal, cardiac and smooth muscles? How do skeletal muscles work in pairs? What is the structure and the components of a muscle, and of a muscle cell (muscle fiber) and the functions of the muscle cell components. 53 54 9
Important Concepts What is the function of tendons? What stimulates a muscle to contract Be able to describe the steps of how the message is transmitted from the neuron to the myofilaments What is the role of Ca 2+. What happens when the message is received by the myofilaments? Important Concepts What are the components of the muscle fibers? Their functions? Be able to identify them in an illustration, including: myofibrils, sarcomeres, Z lines, the myofilaments - actin and myosin filaments, cross-bridges, sarcolemma, sarcoplasm, sarcoplasmic reticulum, T-tubules What are the components and the function of the tropomyosin-troponin complex 55 56 Important Concepts Definitions What are the three energy sources for muscle contraction? Which require oxygen? Which produce carbon dioxide? How many ATP are produced? How long can it provide energy? Muscle fibers Myoglobin Fascia Fascicles Myofibrils Sarcomere Involuntary Voluntary Origin Insertion 57 58 The End Image From: http://guff.com/these-adorable-animal-backsides-will-make-you-smile 59 10